The dictionaries which were sold by Sony operates in pretty much the same manner as the internal dictionary albeit a bit slow on the word retreival. There are also other features such as keeping a list of words that you would want to keep track of as well as being able to select words and "jump" to its definition in the same or other dictionaries. This is particularly useful if you're learning japanese.
The problem however is obtaining one of these memorystick dictionaries because Sony has stopped selling them and the only place you can find it is at the auctions. I got mine at yahoo.
I didn't know that there was a dictionary converter for the Librié though. Perhaps igorsk could kindly provide a link?